﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Security.Cryptography;
using System.Text;
using System.IO;

/// <summary>
/// Summary description for Security
/// </summary>
public class Security
{
    public Security()
    {
        //
        // TODO: Add constructor logic here
        //
    }

    public static string EncryptString(string Message, string Passphrase)
    {
        byte[] Results;
        System.Text.UTF8Encoding UTF8 = new System.Text.UTF8Encoding();

        // Step 1. We hash the passphrase using MD5
        // We use the MD5 hash generator as the result is a 128 bit byte array
        // which is a valid length for the TripleDES encoder we use below

        MD5CryptoServiceProvider HashProvider = new MD5CryptoServiceProvider();
        byte[] TDESKey = HashProvider.ComputeHash(UTF8.GetBytes(Passphrase));

        // Step 2. Create a new TripleDESCryptoServiceProvider object
        TripleDESCryptoServiceProvider TDESAlgorithm = new TripleDESCryptoServiceProvider();

        // Step 3. Setup the encoder
        TDESAlgorithm.Key = TDESKey;
        TDESAlgorithm.Mode = CipherMode.ECB;
        TDESAlgorithm.Padding = PaddingMode.PKCS7;

        // Step 4. Convert the input string to a byte[]
        byte[] DataToEncrypt = UTF8.GetBytes(Message);

        // Step 5. Attempt to encrypt the string
        try
        {
            ICryptoTransform Encryptor = TDESAlgorithm.CreateEncryptor();
            Results = Encryptor.TransformFinalBlock(DataToEncrypt, 0, DataToEncrypt.Length);
        }
        finally
        {
            // Clear the TripleDes and Hashprovider services of any sensitive information
            TDESAlgorithm.Clear();
            HashProvider.Clear();
        }

        // Step 6. Return the encrypted string as a base64 encoded string
        return Convert.ToBase64String(Results).Replace(' ', '+');
    }

    public static string DecryptString(string Message, string Passphrase)
    {
        byte[] Results;
        Message = Message.Replace(' ', '+');
        System.Text.UTF8Encoding UTF8 = new System.Text.UTF8Encoding();

        // Step 1. We hash the passphrase using MD5
        // We use the MD5 hash generator as the result is a 128 bit byte array
        // which is a valid length for the TripleDES encoder we use below

        MD5CryptoServiceProvider HashProvider = new MD5CryptoServiceProvider();
        byte[] TDESKey = HashProvider.ComputeHash(UTF8.GetBytes(Passphrase));

        // Step 2. Create a new TripleDESCryptoServiceProvider object
        TripleDESCryptoServiceProvider TDESAlgorithm = new TripleDESCryptoServiceProvider();

        // Step 3. Setup the decoder
        TDESAlgorithm.Key = TDESKey;
        TDESAlgorithm.Mode = CipherMode.ECB;
        TDESAlgorithm.Padding = PaddingMode.PKCS7;

        // Step 4. Convert the input string to a byte[]
        byte[] DataToDecrypt = Convert.FromBase64String(Message);

        // Step 5. Attempt to decrypt the string
        try
        {
            ICryptoTransform Decryptor = TDESAlgorithm.CreateDecryptor();
            Results = Decryptor.TransformFinalBlock(DataToDecrypt, 0, DataToDecrypt.Length);
        }
        finally
        {
            // Clear the TripleDes and Hashprovider services of any sensitive information
            TDESAlgorithm.Clear();
            HashProvider.Clear();
        }

        // Step 6. Return the decrypted string in UTF8 format
        return UTF8.GetString(Results);
    }

    public static string md5(string sPassword)
    {
        MD5CryptoServiceProvider x = new MD5CryptoServiceProvider();
        byte[] bs = Encoding.UTF8.GetBytes(sPassword);
        bs = x.ComputeHash(bs);
        StringBuilder s = new StringBuilder();
        foreach (byte b in bs)
        {
            s.Append(b.ToString("x2").ToLower());
        }
        return s.ToString();
    }
}